US2540011A

US2540011A - Diazo thioethers

Info

Publication number: US2540011A
Application number: US8736A
Authority: US
Inventors: William B Reynolds; Richard K Harris
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1946-01-17
Filing date: 1948-02-16
Publication date: 1951-01-30
Anticipated expiration: 1968-01-30
Also published as: GB656727A

Description

Patented Jan. 30, 1951 UNITED STATES PATENT OFFICE DIAZO THIOETHERS No Drawing. Original application January 17,

1946, Serial'No. 641,866. Divided and this application February 16, 1948, Serial No. 8,736

12 Claims.

This invention relates to new compounds useful as initiators (catalysts) and modifiers for the polymerization of unsaturated organic compounds either alone or in admixture with one another, and particularly in an aqueous dispersion, which compounds form an important part of the present invention. This application is a division of co-pending application Serial No. 641,866, filed January 17, 1946, now Patent 2,501,692, issued March 28, 1950.

Unsaturated organic compounds capable of undergoing an addition polymerization to form high molecular weight polymers may be advantageously polymerized in the presence of the novel compounds of the present invention either in a homogeneous system or in the form of an aqueous emulsion. Such unsaturated organic compounds are generally those which contain a methylene group attached by an olefinic double bond to a carbon atom in the structure CH2=C Compounds which contain the CH2=C group and are suitable as monomers for use in the process of our invention include the following: butadiene-1,3; its homologues and analogues which polymerize in the same manner, e. g., isoprene, piperylene, chloroprene, etc.; styrene; acrylonitrile; methyl acrylate; methyl methacrylate; vinyl chloride; etc. These unsaturated organic compounds are given by way of example only. The unsaturated organic compounds may conjugated diene hydrocarbon and a monomer copolymerizable therewith in an aqueous emulsion. The aliphatic conjugated diene hydrocarbons (or butadiene hydrocarbons) include butadiene-1,3, isoprene, dimethyl butadiene, piperylene, chloroprene, and the like. Monomers copolymerizable with the aliphatic conjugated dienes in aqueous emulsion systems include aryl olefins and substituted aryl olefins (e; g., styrene,

p-chloro styrene, p-methoxy styrene, vinyl naphthalene, and the like), alkyl esters of acrylic acids (e. g., methyl acrylate, methyl methacrylate, butyl acrylate, and the like); nitriles of acrylic acids (e. g., acrylonitrile, methacrylonitrile, and the like), vinylidine chloride, vinyl ketones (e. g., methyl vinyl ketone), vinyl ethers, vinyl car'- bazole, vinyl furan, vinyl pyridine, and the like, all of which contain the CH2=C group.

An object of this invention is to provide novel compounds, which can be used as initiators, or catalysts, in a process for the addition polymerization of unsaturated organic compounds to form high molecular weight polymers. Another object of this invention is to provide improved initiators or catalysts for use in polymerization reactions of this type. A further object of this invention is to provide compounds particularly suited as initiators and modifiers in the emulsion polymerization of polymerizable organic compounds.

The diazo thio-ethers of the present invention have the general structural formula:

where R is a member of the group consisting of the aromatic and substituted aromatic radicals and R is a member of the group consisting of the aromatic, substituted aromatic, cycloalkyl, substituted cycloalkyl, aliphatic, and substituted aliphatic radicals. These diazo thio-ethers may be made by the combination of a diazotized aromatic amine and an aromatic, cycloalkyl or aliphatic mercaptan, including substituted derivatives.

Examples of aromatic amines which may be used in the preparation of diazo thio-ethers are as follows: aniline, chloroaniline, bromoaniline, toluidine, anisidine, phenetidine, 4-aminodiphenyl ether, dimethoxy aniline, nitroaniline, methyl-methoxy aniline, trimethyl aniline, dichloroaniline, xylidine, chlorotoluidine, naphthylamine, Y dianisidine, benzidine, dichlorobenzidine, sulfanilic acid, aminobenzoic acid, toluidine sulfonic acid, naphthylamine sulfonic acid, and benzidine disulfonic acid. Examples of merc aptans that maybe used as a coupling component in the preparation of diazo thio-ethers are the following: thio-phenol, thio-cresol, chloro thio-phenol, methoxy thio-phenol, thio-salicylic acid, thio-phenol sulfonic acid, thio-naphthol, 2-mercapto-3-naphthoic acid, thio-glycollic acid,

ethyl mercaptan, butyl mercaptan, t-butyl mer- 1 captan, cyclohexyl mercaptan, mercapto benzothiazole, and octyl mercaptan.

The diazo thio-ethers preferred for use as polymerization catalysts in accordance with the present invention are those in which both R- and R. in the foregoing structural formula are aromatic or substituted aromatic groups. EX- amples of preferred compounds are substituted phenyl diazo thio-(naphthyl) ethers, phenyl diazo thio-(phenyl) ethers, naphthyl diazo thio- (phenyl) ethers, and naphthyl diazo thio=(naphthyl) ethers. Preferred substituent groups are the alkyl, alkoxy, aryloxy (e. g., phenoxy), carboxy, sulfo (SOIiH), halo, and nitro' groups; Other substituents give diazo thio-ethers of vary-'- ing degrees of usefulness.

The diazo thio-ethers can conveniently be prepared by diazotizing an aromatic amine and coupling the diazonium compound with an aliphatic or an aromatic mercaptan. Diazo thio-ethers containing two diazo thio-ether groupings. can be prepared by tetrazotizing an aromatic dia mine and coupling the tetrazonium compound with two molecular equivalents of a mercaptan. The coupling to the mercaptan is usually carried out in a strongly alkaline medium although in some examples it is advantageous to carry out the coupling in weakly acidic media. The crude diazo thio-ethers isolated from the coupling are usually of sufficient purity for use in polymerization reactions. However, if a purified product is desired the oil-soluble types may be purified by dissolving in acetone or anhydrous ether at about (3., cooling to about -50 C. and filtering off the recrystallized product. The water soluble type diazo thio-ethers, in the form of their ammonium or alkali metal salts (resulting from coupling in an alkaline medium), can be conveniently purified by washing with anhydrous ether.

New compounds prepared in accordance with this invention which are preferred catalysts for the polymerization process of this inventionare those represented by the formula where Ar is an aryl group and X is a substituent selected from the group consisting of alkyl, alkoxy, aryl and aryloxy radicals, n is an integer from one to four, n being at least two when a methyl radical is a substituent; and R. is a member of the group consisting of aromatic, sub-- stituted aromatic, cycloalkyl, substituted cyclo alkyl, aliphatic, and substituted aliphatic radi cals. When a methyl substituent is employed in the aryl group attached to the nitrogen at least one other methyl (or other alkyl), alkoxy, aryl. or aryloxy radical is also present. Specific examples of new compounds forming a part of our invention are the following: p-methoxy phenyl diazo thio-(Z-naphthyl) ether, dimethyl phenyl diazo thio-(2-naphthyl) ether, dimethyl phenyl diazo thio-(p-methoxy phenyl) ether, p-methoxy phenyl diazo thio-(o-carboxy phenyl) ether, p-

sulfo phenyl diazo thio-(2--naphthyl) ether, p-

sulfo phenyl diazo thio-(p-tolyl) ether, 2-naphthyl diazo thio-(carboxy phenyl) ether, and the like, together with the ammonium and alkali metal salts of such compounds. Some of the more important new compounds may be conveniently represented by the formula where X is a substituent selected from the group consisting of alkoxy and aryloxy radicals, n is an integer from one to four, and R is a member of the group consisting of aromatic, substituted aromatic, cycloalkyl, substituted cycloalkyl, aliphatic, and substituted aliphatic radicals.

Conventional practice in emulsion polymerizations has been to add together a monomer or mixture of monomers capable of being polymerized, one or more of various initiatorsy'catalysts, and modifiers, water and an emulsifying agent. The initiator used generally is either an organic peroxide or an inorganic peroxidic material, usually used incombination with a modifying agent such as a mercaptan. In one commonly used system a water-soluble oxidant such as potassium persulfate is used in conjunction with an oil-soluble mercaptan which according to theory is oxidized, possibly in the aqueous or soap phase to a mercaptan free-radical, which initiates polymer chain growth by combining with a monomer unit. There are certain inherent defects in such a chain initiation system; and furthermore, the use of an oxidant such as potassium persulfate may have certain undesirable features inasmuch as the oxidant is likely to enter into certain undesirable side reactions.

We' have now discovered that the defects of the above described system, which nevertheless is the best system previously known, can be large- 13 overcome through the use of diazo thio-ethers as polymerization initiators. Furthermore the diazo thio-ethers have the great advantage of functioning also as modifiers of chain growth, thus making it possible to control the molecular weight and properties of the polymer without the use of additional modifiers. However, it is sometimes advantageous to use supplementary modifiers in addition to the diazo thio-ether.

Although the exact mechanism of chain initiation by diazo thio-ethers is not known-it is possible that the chains are initiated by free radicals formed by decomposition of the diazo thio-ether. Free radicals can be formed, for example, according to the following reaction:

Either or both of the above free radicals might then initiate polymer chain growth by reacting with a monomer unit according to reactions such as the following:

RCH=CI-I2+R'S- R-CHCH2SR RLCH =CH2+R- RH+R-CH=CH The mechanism of the chain-transfer function of the diazo thio-ethers is likewise not clearly understood. The chain-transfer may be brought about by mercaptans generated by decomposition of the diazo thio-ether. However, it may also be that the diazo thio-ether, itself, is a chaintransfer agent according to either or both of the following reactions where R represents a growing polymer molecule:

units thus initiating new polymer chains.

The theory set forth above is a possible explanation of the mechanism involved in the function of diazo thio-ethers of our invention in emulsion polymerization reactions. This theory is included herein only as an aid in understanding the present invention and is not to be construed as in any way limiting the invention. Regardless of the mechanism postulated, the fact remains that the diazo thio-ethers effectively catalyze and modify emulsion polymerization reactions.

One of the greatest advantages of the use of diazo thio-ethers in polymerization reactions in accordance with our invention is their great versatility. V Diazo thio-ethers of almost any desired reactivity canbapreparedby suitably varying the radicals R and R. For example, if R and R are both aromatic radicals, diazo thio-ethers of great activity can be obtained if either or both to prepare water soluble diazo thio-ethers it is only necessary that either or both of the radicals R or R contain a water solubilizing substituent, for example, the carboxylic or sulfonic acid groups or other hydrophilic groups. soluble diazo thio-ethers are conveniently prepared and used in the form of their ammonium or alkali metal salts. In general the initiator activity of the water soluble diazo thio-ethers may be said to be somewhat greater than that of comparable oil soluble diazo thio-ethers. However, both types appear to be of similar efiiciency as polymerization modifiers.

The type and amount of diazo thio-ether used in a particular polymerization recipe depends upon the result desired. For polymerizations to be carried out at low temperatures (e. g., -10 to 40 C.) an active diazo thio-ether is chosen. The water soluble types are particularly satisfactory for low-temperature recipes. In carrying out polymerization in an aqueous emulsion at a temperature below the freezing point of the aqueous phase, an inert freezing point depressant is employed. For polymerizations to be carried out at higher temperatures (e. g.-, 40-60 C.)

diazo thio-ethers of moderate activity are chosen while for even higher temperature polymerizations diazo thio-ethers of low activity are selected. In general, approximately 0.2 part by weight of the diazo thio-ether, based on the weight of the monomeric material, will give satisfactory promotion although other proportions within the range of about 0.05 to about 5.0 parts by weight, based on the weight of the monomeric a dodecyl mercaptan to the polymerization recipe.

Typical examples of our invention are the following:

Earample I 123 parts of p-anisidine are dissolved in 3,000 parts of water with 91 parts of hydrogen chloride (100%) used as 36% solution. The resulting solution is cooled to to C. and diazotized by the addition of 70 parts of sodium nitrite dissolved in 200 parts of water. The diazonium solution is poured rapidly into a solution of 163 parts of thio-beta-naphthol andj400 parts of sodium hydroxide in 4,500 parts of water at Such water 0.150 5 C. The diazo thio-ether, p-methoxy phenyl diazo thio-(2-naphthyl) ether, immediately precipitates as a finely dispersed oil, which soon solidifies to a yellow solid. The solid material is filtered off, washed thoroughly, and

dried at room temperature under vacuum. This thio-ether is oil soluble.

Two parts of the diazo thio-ether are added to an agitated autoclave containing water 180 parts, soap 5 parts, butadiene '75 parts, and styrene 25 parts. Agitation is continued for nine hours while the charge temperature is maintained at 50 C. by means of water circulation in the autoclave jacket. At the end of nine hours the charge is discharged into a stripping tank where the unreacted monomers are recovered bysteam distillation. The latex is creamed by the addition of a small amount of sodium chloride solution and coagulated by the addition of dilute sulfuric acid. The rubber crumb is washed several times by decantation and, finally, dried in a vacuum oven at 60 C. The product, which is thus obtained in about conversion based upon the weight of starting monomers, is a soft, well-modified rubber which is soluble in benzene and has good properties when compounded and vulcanized in conventional ways.

Example II parts of beta-naphthylamine are diazotized in 2,000 parts of water containing 250 parts of 10 N hydrochloric acid by the addition of a solution of '70 partsof sodium nitrite. The resulting diazonium solution is run slowly into a solution of 162 parts of thio-salicylic acid in 10,000 parts of" water containing 80 parts of sodium hydroxide and 410 parts of sodium carbonate. The sodium salt of beta-naphthyl diazo thio-salicylic acid precipitates and is filtered and washed thorough- 1y with 10% sodium sulfate solution and, finally, once with a small amount of cold water. The product, 2-naphthy1 diazo thio-(carboxy phenyl) ether, is dried at room temperature under vacuum. If desired it can be purified by washing with a little anhydrous ethyl ether. The resulting product is of the water soluble type.

When used in a polymerization recipe-essentially as described in Example I, the results are comparable to those of Example I.

Example III 1'73 parts of sulfanilic acid are .diazotized in 2,000 parts of water containing 25 parts of 10 N hydrochloric acid by the addition of a solution of 70 parts of sodium nitrite. The cold diazonium solution is poured rapidly into a cold solution of 131 parts of p-thio-cresol in 5,000 parts of water containing 80 parts of sodium hydroxid and 82 parts of sodium acetate. The bright, yellow sodium salt of the diazo thio-ether precipitates immediatel and is isolated, washed, and dried as in Example II. Thi product, p-sulfo phenyl diazo thio-(p-tolyl) ether, is of the water soluble type.

One part of the diazo thio-ether is added to-a polymerization mixture containing parts of water, 5 parts of Aerosol AY (a commercial, synthetic detergent described as a succinic ester sulfonate), '75 parts of butadiene, and 25 parts of styrene. Polymerization is carried out at 50 C. for 12 hours and the rubber isolated by methods analogous to those of Example I.

Example IV amogom 7 ie sale, p-me'tho'xy lzphenyl fdiazo thio-(e'arboxy) "DhenyD ether, "(a *diazo thiotherpf the water soluble type), are added to a polymerization recipe containing 180 Iparts of water, .5 parts of Aerosol AY, 75 parts of butadiene, and 25 .parts o'f styr'ehe. Polymerization is carriedout at 25 C. for twelve hours and the product isolated as in Example I. A wen 'mo'difie'd rubber of .good properties is obtained.

Example V 053 part "of the diazothio-ether of Example 51 is added to a polymerization recipe containing 180 parts of water, 5 parts of soap, 04 part of dodecyl mercaptan, '75 arts of butadiene and 25 parts of styrene. Polym'eriz'ation i continued for 12 hours at 50 C. and the product isolated as in Example -I. Aw'ell modified :ru'bber 01 good properties is'obtained.

Example V1 '03 part of "the diazo'thio-ether'of Example Iis added to a polymerization recipe containing 180 parts of water, 5 parts of soap, 0.2 partof potassium persulfa tejwl part of tertiar dodecyl mercaptan, '75 parts o'f'butadieneand 25 parts of styrene. Polymerization is continued for hours and the rubber isolated as in Example I.

Example -VII An'aut'oclaveiis charged exactlyas in Example I except that is'oprene is used in place of the butadi'ene. A comparable rubber "of very good properties isobtain'ed.

Example VIII Two parts of the diazo'thio-ether'of Example I are added to a polymerization mixture of water 180 parts, soap 5 .parts, butadiene 75 parts and methyl methacrylate parts. Polymerization proceeds rapidly at 50 C. to give an elast'or'ner having certain very desirable'properties.

Example IX One part of the di'azo thio-ethero'f Example l i added to '100 parts of ethyl acrylate. The -so lution 'is run slowl into an agitated autoclave containing 150 parts of water and one part of Aerosol AY, thebatch temperature being maintained at 50 C. 'An acrylic polymer of valuable properties is obtained.

Example X One part of the oil soluble diazo thio-"ether,.pchloro phenyl diazo thiO-(Z-naphthyl) ether, prepared by coupling diazotized p-chloroaniline with thio-beta-naphthoLis dissolved in 100 parts of methyl methacrylate and polymerized .ia's in Example IX. -A methacrylate 'poylm'er -of valuable properties is obtained.

Example XI Two parts of the diazo thio-ether of Example I are added "to a polymerization recipe of "180 parts of water, 5 partsof soapjfloparts 'of'butadiene and parts of'acrylonitrile. Polymerization is-carried 'out at5'0' 'C. andthe product isolated 'asin Example" I.

Example Jill A polymerizatio'nis carried out exactly as in Example I except that vinyl pyridine is used in .place of styrene. Awell modified rubber ofsgood -Pt opertiesis-obtained.

Example XIII A polymerization is carried out exactly as in Example I except that dichlorostyrene is used in -place of styrene. A well modified rubber of gOOd prope'rties is obtained.

Example XI-V Two parts of the diazo thio-ether prepared in Example I are added to a polymerization mixture consisting of 180 parts of Water, 5 parts of dodecyl ammonium acetate, parts of butadiene and 25 parts of styrene. Polymerization is carried out at 40 C. The stripped latex is coagulated, isolated and driedin the usual way.

Example XV 05 part of the diazo thio-ether, dimethyl phenyl diazo thio (2.-naphthyl) ether, prepared bycoupling 'diazotized m-xylidine with thio-betanaphthol is added to a polymerization mixture containing parts of water, '5 parts of soap, '75 parts of butadiene and 25 parts of styrene. Polymeriza'tion is carried-out at 50 C. for 3 hours to obtain a 65% conversion ofa soft, well-modified rubber of good properties. When the diazo thioether was replaced'by 0.3 part of potassium persulfateand 0.5 part of dodecyl mercaptan in the abov recip'e, ten hours were required to effect the same amount of conversion.

Example XVI The polymerization of Example I was carried outin which a total of 0.75 part'of the diazo thioether was added in increments as the polymerization proceeded. 0505 part of the promoter was added at the beginning of the reaction, 0.3 part was added at the end of one hour and 0.4 part was added at the end of four hours. Polymerization "conversion was 75% "in seven hours at 50 .C. The'rubber was completely soluble in benzeneiand had 'very good properties. This increiment'manner of addition was found to decrease materially theproportion of diazo thio-ether'required' while providing uniform modifying action. I he foregoing examples illustrate preferred methods of practicing this-invention and are to be construed as being illustrative only, without inany'way limiting the scope of the invention.

-An impor-tant advantage of the process of this invention-and the catalysts employed therewith is illustrated in the examples illustrating the use of dia'zo thio-ethers of both the oil-soluble and the water-soluble types. "The choice o'f the diazo thio-ether also effects the rate of polymerization as is illustrated in the examples. Catalysts of our invention may be employed to efiectvery rapid polymerization of the monomeric materials, if desired, and make possible continuous emulsion polymerization in lieu of th conventional batch process.

present invention are found to have excellent z'proper-ties when "evaluated .in icomp'arison with standardsynthetic'rubbers in conventional compounding-recipes. Standard tread stocks'prepared from lpolymers made in accordance with the pres- 'ent invention have room temperature tensile trengths in the range Tof 3000 to 35001poun'cls:per

square inch or more and room temperature elongations in the range of 600 to 800 per cent or more. Other properties such as hysteresis, flex life, abrasion resistance, etc., of the products of the present invention in many cases possess definite superiority over polymers produced by conventional methods.

Although we have disclosed specific embodiments of our invention, it will be apparent that the initiators and polymerization process of our invention are capable of broad application in the art, and that various modification may be made without departing from the scope of the invention.

We claim: V

1. Diazo thio-ethers represented by the formula R-N=N-SR' where R is of the group consisting of naphthyl, dimethylphenyl, methoxyphenyl, chlorophenyl, and sulfophenyl, and R is of the group consisting of naphthyl, methylphenyl, methoxyphenyl, and carboxyphenyl.

2. Sulfo phenyl diazo thio-tolyl ether.

3. p-Sulfo phenyl diazo thio-(p-tolyl) ether.

4. Chloro phenyl diazo thio-naphthyl ether.

5. p-Chloro phenyl diazo thio-(2-naphthyl) ether.

6. Methoxy phenyl ether.

7. p-Methoxy phenyl diazo thio-(naphthyl) ether.

diazo thio-(naphthyl) diazo thio- (naphthyl) 12. p-Methoxy phenyl diazo thio-(carboxy phenyl) WILLIAM B. REYNOLDS. RICHARD K. HARRIS, Administrator of the Estate of Ernest W. Gotten,

Deceased.

REFERENCES CITED The following. references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,251,156 Nygaard .a July 29, 1941 2,376,963 Garvey May 29, 1945 OTHER REFERENCES Chem. Abst., v01. 22,page 4465 (1928), citing Finzi-Gazzetta Chimica Italiana, vol. 58, pp. 269- 278 (1928).

Berichte Deut. Chem., Vol. 28. pages 3237 to 3251 (1895).

Claims

1. DIAZO THIO-ESTHERS REPRESENTED BY THE FORMULA R-N=N-S-R'' WHERE R IS OF THE GROUP CONSISTING OF NAPHTHYL, DIMETHYLPHENYL, METHOXYPHENYL, CHLOROPHENYL, AND SULFOPHENYL, AND R'' IS OF THE GROUP CONSISTING OF NAPHTHYL, METHYLPHENYL, METHOXYPHENYL, AND CARBOXYPHENYL.